linux-kernel - RE: [PATCH] cpufreq, intel_pstate, set max_sysfs_pct and min_sysfs

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Date:	Wed, 7 Oct 2015 11:52:42 -0700
From:	"Doug Smythies" <dsmythies@...us.net>
To:	"'Prarit Bhargava'" <prarit@...hat.com>
Cc:	"'Kristen Carlson Accardi'" <kristen@...ux.intel.com>,
	<linux-kernel@...r.kernel.org>,
	"'Viresh Kumar'" <viresh.kumar@...aro.org>,
	<linux-pm@...r.kernel.org>,
	"'Rafael J. Wysocki'" <rjw@...ysocki.net>,
	"Doug Smythies" <dsmythies@...us.net>
Subject: RE: [PATCH] cpufreq, intel_pstate, set max_sysfs_pct and min_sysfs_pct on governor switch

On 2015.10.07 08:46 Prarit Bhargava wrote:
> On 10/07/2015 11:40 AM, Doug Smythies wrote:
>> 
>> Do we agree or disagree that the root issue seems to be (from your test)?:
>> 
>> \#  echo 100 > /sys/devices/system/cpu/intel_pstate/min_perf_pct
>> 
>> [   21.483436] store_min_perf_pct[453] min_sysfs_pct = 100
>> [   21.489373] store_min_perf_pct[456] min_perf_pct = 100
>> [   21.495203] store_min_perf_pct[459] min_perf_pct = 100
>> [   21.501050] store_min_perf_pct[462] min_perf_pct = 100
>
> Yep, and it appears to be done by default in Fedora & RHEL :/ ... the issue is
> still the same IMO that min_sysfs_pct & max_sysfs_pct are not cleared on a
> governor switch.

Clearing them will break some other things. For example, and as
shown in my original reply, resume from suspend.

Why? Because, at least on my computer, the governor is changed to
"performance" during suspend, and the "powersave" governor is
restored sometime during resume. The users wants the settings they had
before the suspend.

Continuing with that printk debug kernel from earlier:

pm-suspend:

[12599.912028] intel_pstate_set_policy[1001] min_perf_pct = 100
[12599.913781] intel_pstate_set_policy[1001] min_perf_pct = 100
[12599.915343] intel_pstate_set_policy[1001] min_perf_pct = 100
[12599.916877] intel_pstate_set_policy[1001] min_perf_pct = 100
[12599.918444] intel_pstate_set_policy[1001] min_perf_pct = 100
[12599.919686] intel_pstate_set_policy[1001] min_perf_pct = 100
[12599.920932] intel_pstate_set_policy[1001] min_perf_pct = 100
[12599.922191] intel_pstate_set_policy[1001] min_perf_pct = 100

Then push the power button, i.e. resume:

[12609.953358] intel_pstate_set_policy[1020] min_perf_pct = 50
[12609.953360] intel_pstate_set_policy[1023] min_perf_pct = 50
[12609.953361] intel_pstate_set_policy[1028] min_perf_pct = 50
[12609.953796] intel_pstate_set_policy[1020] min_perf_pct = 50
[12609.953797] intel_pstate_set_policy[1023] min_perf_pct = 50
[12609.953798] intel_pstate_set_policy[1028] min_perf_pct = 50
[12609.954209] intel_pstate_set_policy[1020] min_perf_pct = 50
[12609.954210] intel_pstate_set_policy[1023] min_perf_pct = 50
[12609.954211] intel_pstate_set_policy[1028] min_perf_pct = 50
[12609.954619] intel_pstate_set_policy[1020] min_perf_pct = 50
[12609.954620] intel_pstate_set_policy[1023] min_perf_pct = 50
[12609.954621] intel_pstate_set_policy[1028] min_perf_pct = 50
[12609.955028] intel_pstate_set_policy[1020] min_perf_pct = 50
[12609.955029] intel_pstate_set_policy[1023] min_perf_pct = 50
[12609.955030] intel_pstate_set_policy[1028] min_perf_pct = 50
[12609.955431] intel_pstate_set_policy[1020] min_perf_pct = 50
[12609.955432] intel_pstate_set_policy[1023] min_perf_pct = 50
[12609.955433] intel_pstate_set_policy[1028] min_perf_pct = 50
[12609.955833] intel_pstate_set_policy[1020] min_perf_pct = 50
[12609.955834] intel_pstate_set_policy[1023] min_perf_pct = 50
[12609.955835] intel_pstate_set_policy[1028] min_perf_pct = 50
[12609.956234] intel_pstate_set_policy[1020] min_perf_pct = 50
[12609.956235] intel_pstate_set_policy[1023] min_perf_pct = 50
[12609.956235] intel_pstate_set_policy[1028] min_perf_pct = 50

The below is copied from my original reply:

Before Patch, I get:

root@s15:/home/doug/temp# grep . /sys/devices/system/cpu/intel_pstate/*_perf_*
/sys/devices/system/cpu/intel_pstate/max_perf_pct:80
/sys/devices/system/cpu/intel_pstate/min_perf_pct:50
root@s15:/home/doug/temp# pm-suspend
...
root@s15:/home/doug/temp# grep . /sys/devices/system/cpu/intel_pstate/*_perf_*
/sys/devices/system/cpu/intel_pstate/max_perf_pct:80
/sys/devices/system/cpu/intel_pstate/min_perf_pct:50

After Patch, I get:

root@s15:/home/doug/temp# grep . /sys/devices/system/cpu/intel_pstate/*_perf_*
/sys/devices/system/cpu/intel_pstate/max_perf_pct:80
/sys/devices/system/cpu/intel_pstate/min_perf_pct:50
root@s15:/home/doug/temp# pm-suspend
...
root@s15:/home/doug/temp# grep . /sys/devices/system/cpu/intel_pstate/*_perf_*
/sys/devices/system/cpu/intel_pstate/max_perf_pct:100
/sys/devices/system/cpu/intel_pstate/min_perf_pct:42


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